Physics
Fluid-Mechanics
Easy
Question
A cylinder containing water upto a height of 25 cm has a hole of cross section at its bottom. It is counter passed in a balance. When water begins to flow out, the initial change in the balancing weight is
- Increase of 12.5 gm wt
- Increase of 6.25 gm wt
- Decrease of 12.5 gm wt
- Decrease of 6.25 gm wt
The correct answer is: Decrease of 12.5 gm wt
Let v be the initial velocity of efflux of water.
Initial volume of water flowing out per sec = av
Initial mass of the water flowing out per sec
Rate of change of momentum
Initial downward force on the out flowing water = av2
Reaction acts upwards on the cylinder
Initial upward reaction = av2
Initial decrease in weight
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